September time to take critical lawn care steps

“Wait until September,” I keep saying pretty much all summer. With the wet spring and early summer we had, fungus diseases on lawns have been common, especially on lawns that receive generous amounts of nitrogen.

Although some fungus diseases respond well to fungicides — typically applied by a certified applicator — many do enough damage that waiting until September is the thing to do.

At this time — and now is the time — lawns can be repaired or renovated. It takes the cooler temperatures and some rain to make for a successful recovery. Germination and seedling survival are all favored by those early fall conditions. Plus the work is easier on you when temperatures are cooler.

Weed control, fertilizing

No lawn damage to rescue? No problem. Fall is also the best time to fertilize and apply broadleaf weed control. If you only fertilized or applied broadleaf weed control one time during a year, this would be the time. Replicated research bears this out, and fall application has been a standard recommendation from the Purdue Extension Turf Specialists for many years.

On the fertilizer front, using a fall formulation in September and November gives a lawn the resilience and nutrients it needs to get all the way to May when — we hope — the spring rains have let up. You are reading this right: skip the so-called March “green-up” application. It only invites fungal disease and extra mowings. If you are applying a pre-emergent crabgrass control in March, make it a solo application and skip the fertilizer.

On the weed-control front, those broadleaf weed control materials are much more effective when the weeds are translocating nutrients downward, as they do in the fall. Spring applications are less effective. For more on this see Purdue Extension’s “Seven Simple Steps to a Better Home Lawn” (

Lawns needing more help

A lawn damaged by fungus may need just some patching here and there, or a complete renovation. With either approach, some things are critical:

  • Adequate soil moisture
  • Good seed-to-soil contact, which comes from a well-prepared seedbed.
  • Seed protection — from drying or disturbance.

If you are using a patch product, follow the instructions on the package. Some patch products include a fiber mulch, but you can also use straight seed and a cover such as straw or grass mat. You can select seed for your growing conditions, or choose a mix that may waste some seed but covers a variety of conditions.

A total lawn renovation gets easier when you use a slit-seeder. This gets you out of the business of tilling up an entire yard, which has many downsides. Slit-seeders can be rented, or you can find a lawn care contractor to do the work. If you decide to work with a contractor, consider at least two quotes in writing, capturing who will be responsible for cleanup or repairs. For more on lawn renovation, see Purdue Extension’s “Lawn Improvement Programs” (

Fertilizer management does much to prevent fungal disease on lawns. Keep nitrogen application down to 3 to 3½ pounds per thousand square feet per year, and avoid many of the troubles that come with overapplied nitrogen. If you are making applications yourself, you can do the math based on the product label. If a lawn care company is making the applications, they should be able to tell you. Just bear in mind that soft, juicy plant tissue oversupplied with nitrogen signals “Dinner!” to the pests.

Kris Medic is Purdue Extension Bartholomew County’s educator for agriculture, natural  resources and community development. She can be reached at 812-379-1665 or